Ion traps have been used for the study of spectroscopic and other physical properties of ions. Linear ion traps, in which ions are confined radially by a two-dimensional radio frequency (RF) field and axially by stopping potentials applied to end electrodes, are rapidly finding new applications in many areas of mass spectrometry. In U.S. Pat. No. 4,755,670, Syka and Fies have described the theoretical advantages of 2-D versus 3-D quadrupole ion traps for Fourier transform mass spectrometry. These advantages include reduced space charge effects due to the increased ion storage volume, and enhanced sensitivity for externally injected ions due to higher trapping efficiencies.
Recently, there has been a significant amount of work performed on techniques for increasing sample throughput for mass spectrometers. Currently, the most commercially popular technique is through serial multiplexing, where a modified ion source with multiple independent sprayers is used and a mechanical mask blocks all but one of the sprayers at a time. The mask switches sequentially from sprayer to sprayer to acquire mass spectra from each sample in a serial fashion. The primary disadvantage of the serial multiplexing technique is the reduced sampling rate for each sample. For example, with a four-sprayer ion source, each sprayer is sampled at a rate that is 4 times slower than that of a standard instrument.
Accordingly, further developments in the field are needed.